RU2502049C1 - Small-size platformless inertial navigation system of medium accuracy, corrected from system of air signals - Google Patents

Abstract

FIELD: instrument making.

SUBSTANCE: invention may find application in inertial navigation systems (INS) of aviation and ground carriers. Two computing navigation platforms are used, each of which generates its own control law (damping of inertial errors), depending on parameters of carrier movement, and namely, on components of horizontal accelerations of the carrier. At the same time the first platform provides for numeration of angles of pitch and tilt of the carrier orientation, and the same time - a course angle, and calculation of projections of carrier speeds and is geographic coordinates, with account of preliminary determined and memorised estimates of wind speed and direction.

EFFECT: increased accuracy of numeration of speeds and coordinates of a moving object with a small-size platformless INS of medium accuracy in an autonomous mode without use of permanently updated signals of an operating satellite navigation system in real time.

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Description

Technical field

The invention relates to the field of small-sized strapdown inertial navigation systems (SINS) for a different class of carriers from aviation to ground.

State of the art

The use of small-sized SINS with “coarse” and medium-precision sensitive elements (SE) is described in a number of US patents of American GNC Corporation, for example, in a number of patents on small-sized micromechanical inertial measuring devices (US Patent Nos. 6671648, 6522992, 6516283) and on methods for processing measurements media motion parameters with their use (US Pat. Nos. 0697758, 6651027, 6494093, 6473713, 6427131). The main focus of these patents is on providing advantages over conventional traditional SE units based on the use of external navigation information sensors (such as GPS), the use of error damping of the computing platform, etc.

The main drawback of the SINS data is the impossibility of long-term operation in stand-alone mode when the satellite navigation system (SNA) is turned off, which is fundamentally important, for example, when setting active interference of any type (the so-called “GPS jamming”) for the SNA. In the presence of jamming type interference, the SINS becomes completely inoperative in the integrated (joint with the SNA) mode, as the external navigation information used to damp the calculation errors is lost. At the same time, errors in determining coordinates reach unacceptable values of the order of tens of kilometers.

The closest analogue (prototype) to the proposed device is a small-sized SINS targeting "coarse" CE (copyright patent of the Russian Federation No. 2382988, IPC G01C 23/00, published on 02.27.2010). This system performs error damping using the difference between the SINS accelerations and the air signal system (SHS).

The main limitation of such a SINS is the fact that it does not reckon velocities and coordinates, but determines only orientation angles. Damping by the difference in accelerations used in the prototype cannot be used to determine the coordinates, since it leads to unacceptably large errors in determining the velocities, and hence the coordinates when integrating velocities, while quite reasonable accuracy is provided for orientation angles.

Disclosure of invention

The main objective of the invention is a significant increase in the accuracy of calculating the speeds and coordinates of a moving object with small SINS of medium accuracy in offline mode without the use of constantly updated real-time signals of the working SNA. Using the components of wind speed and airspeed, it is possible to determine the speed of an object relative to the Earth in the absence of true signals from the SNA (primarily in the presence of active interference of any type of SNA - “jamming”).

The technical result is achieved by the fact that in the SINS two computational navigation platforms are implemented, each of which has its own control law (damping of inertial errors), which depends on the parameters of the carrier’s movement, namely, on the components of the horizontal accelerations of the carrier. The first platform is a traditional unperturbed computing platform, but with its own acceleration damping. The second provides error damping by the difference in the speed readings of the ANN and the air signal system (SHS). In this case, preliminary, in the presence of SNA signals, the error of the non-alignment of the ANN in azimuth, the speed and direction of the wind are determined. The first platform provides the calculation of the pitch and roll angles of the carrier’s orientation, while the second provides the angle of the course and the projection of the projection of the carrier’s velocities and its geographical coordinates, taking into account predefined and remembered estimates of the wind speed and its direction.

The small-sized SINS of medium accuracy, correctable from the air signal system, contains a block of sensitive elements (SE) of medium accuracy, consisting of three accelerometers and three angular velocity sensors along three orthogonal axes, two computing platforms, an air signal system, a heading error determination unit, and a determination unit wind speed; communication with the satellite navigation system, while the outputs of the linear acceleration signals of accelerometers and angular velocities of the SE block, as well as the output of the air signal system, respectively, are connected to the first, second and third inputs of the first and second computing platforms, the output of the air signal system is also connected to the first input of the block determination of wind speed; the satellite navigation system is connected to the first input of the heading error determination unit and to the second input of the wind speed determining unit, the output of which is connected to the fourth input of the second computing platform, the output of which is connected by the speed of the medium to the second input of the heading error determining unit, the output of which is connected to the fifth input the second computing platform, the outputs of which are the outputs of the system in the course angle, speed and geographical coordinates of the medium, and the outputs of the first computing platform are the outputs s system for pitch and roll carrier.

As part of the first computing platform, there is its own unit for converting accelerations from the coordinate system connected to the navigation system, its own unit for calculating the linear and angular velocities of the navigation coordinate system, its own block for generating damping signals, its first and second blocks for quaternion computing, its own unit for computing the matrix of guiding cosines and orientation angles ; own connection with the air signal system; wherein the output of the linear acceleration signals of the accelerometers of the SE unit is connected to the first input of the acceleration conversion unit, the output of which is connected to the input of the speed calculation unit of the navigation coordinate system and the first input of the damping signal generation unit; the output of the angular velocity signals of the SE block is connected to the first input of the first quaternion block, the output of which is connected to the first input of the second quaternion block; the second and third inputs of which are connected respectively to the output of the speed calculation unit of the navigation coordinate system and to the output of the damping signal generation unit; the output of the second quaternion block is connected to the input of the block calculating the matrix of guide cosines, as well as in feedback with the second input of the first quaternion block; the first feedback output of the computing block of the matrix of guide cosines is connected to the second input of the acceleration conversion unit; the output of the air signal system is connected to the second input of the damping signal generation unit; the second and third outputs of the block of calculation of the matrix of guide cosines are the outputs of the first computing platform and the entire system at the pitch and roll angles of the carrier.

As part of the second computing platform, its own unit for converting accelerations from the coordinate system connected to the navigation system, its own block for calculating linear and angular velocities and geographical coordinates, its own block for generating damping signals, its first and second blocks for quaternion calculations, its own block for computing the matrix of guiding cosines and orientation angles ; its connections with the airborne signal system, with the unit for determining wind speed and with the unit for determining heading error; wherein the output of the linear acceleration signals of the accelerometers of the CE unit is connected to the first input of the acceleration conversion unit, the output of which is connected to the first input of the speed and coordinate calculation unit; the output of the angular velocity signals of the SE block is connected to the first input of the first quaternion block, the output of which is connected to the first input of the second quaternion block, the second, third, and fourth inputs of which are connected respectively to the first output of the block of speed and coordinate calculations; with the first output of the damping signal generating unit and with the output of the heading error determination unit; the output of the second quaternion block is connected to the input of the block calculating the matrix of guide cosines, as well as in feedback with the second input of the first quaternion block; the feedback output of the computing block of the matrix of guide cosines is connected to the second input of the acceleration conversion unit; the output of the air signal system is connected to the first input of the damping signal generation unit; the output of the block for computing the matrix of guide cosines along the angle of the carrier course is connected to the input of the block for determining wind speed and to the second input of the block for generating damping signals; the signal of the projections of the airspeed according to the SHS is fed from the second output of the damping signal generation unit to the first input of the first adder, the second input of which is connected to the output of the stored estimates of the projections of the wind speed of the wind speed determination unit, and the output of the first adder is connected to the first input of the second adder, to the second whose input with a minus sign is the signal of projections of the carrier velocity from the second output of the speed and coordinate calculation unit; and the output of the second adder is connected to the third input of the damping signal generation unit and to the second input of the speed and coordinate calculation unit, the second and third outputs of the speed and coordinate calculation unit, respectively, from the projections of the carrier speed and the geographical coordinates of the carrier, as well as the output of the calculation unit of the guide cosine matrix in the angle of the carrier course are the outputs of the second computing platform and the entire system.

List of drawings

Figure 1 is a block diagram of the hierarchy levels of the device of the proposed system.

Figure 2 - block diagram of the device of the first computing platform.

Figure 3 - block diagram of the device of the second computing circuit of the device.

Figure 4 is a stage timing diagram of the system.

Figure 5 is a comparison of time graphs of errors in determining the coordinates of the proposed device and prototype.

The implementation of the invention

In Fig. 1 ... 3, the system blocks have the following end-to-end numbering: 1 - a block of sensitive elements consisting of three accelerometers and three angular velocity sensors located along three orthogonal axes, 2 - an air signal system, 3 - a satellite navigation system, 4 - 1 -th computing platform, 5 - 2nd computing platform, 6 - unit for determining the course error, 7 - unit for determining the wind speed; in the first computing platform, 4: 8 is a unit for converting accelerations from the coordinate system connected to the navigation system, 9 is a unit for calculating linear and angular velocities of the navigation coordinate system, 10 is a damping signal generation unit, 11 is a first block of quaternion calculations, 12 is a second block of quaternion calculations 13 - block for calculating the matrix of guide cosines and orientation angles, in the second computing platform 5: 14 - block for recalculating accelerations from the coordinate system connected to the navigation system, 15 - block for calculating linear and angles x speeds and geographical coordinates, 16 - block for generating damping signals, 17 - first block for quaternion calculations, 18 - second block for quaternion calculations, 19 - block for calculating the matrix of guiding cosines and orientation angles, 20 - first adder, 21 - second adder.

In the drawings, the following designations of the device signals are adopted:

from block 1: a _b is the vector of signals of apparent acceleration from accelerometers and ω _b is the vector of signals of the absolute angular velocity of the TLS in the associated coordinate system;

носителя, измеренная СВС;from block 2: V _CHC - airspeed (projection (components) of speed

media measured by SHS;

from block 3: V _CHC - ground speed measured by SNA (velocity projection (V _N , V _E ));

- оценка ошибки курса;from block 6:

- assessment of course error;

- оценка скорости ветра (составляющие (проекции) скорости U_N, U_E),

- оценка направления ветра.from block 7:

- assessment of wind speed (components (projections) of speed U _N , U _E ),

- assessment of wind direction.

Projections of any speeds with indices N, E are projections on the axis of the navigation coordinate system.

- управляющая угловая скорость для демпфирования ошибок платформы,

- матрица направляющих косинусов, (q₀, q₁, q₂, q₃)_i - кватернион поворота от связанной к навигационной системе координат,On the block diagrams of computing platforms (index i = 1, 2 corresponds to the platform number): a _Ni is the acceleration and ω _Ni is the angular velocity of the carrier in the navigation coordinate system,

- control angular velocity for damping platform errors,

is the matrix of guide cosines, (q ₀ , q ₁ , q ₂ , q ₃ ) _i is the quaternion of rotation from the coordinate system connected to the navigation,

V ₂ - the path speed of the carrier at the output of the system (V _N2 , V _E2 - projection of speed),

φ ₂ , λ ₂ - geographical coordinates (latitude and longitude) obtained by the system.

ϑ _i , γ _i , H _i - orientation angles, respectively, of pitch, roll and heading of the carrier,

Information and signal exchange between the inputs and outputs of the blocks is carried out along the communication lines shown on the block diagrams by solid thin lines. Communication lines are known lines of communication and information exchange, for example, via serial code, parallel code, multiplex, etc. Various digital and analog channels can be used as data transmission channels, for example, information exchange channels made in accordance with GOST 18977 -79 (Airborne equipment and helicopter complexes. Types of functional communications. Types and levels of electronic signals).

System device

To improve the accuracy and efficiency of the autonomous determination of current navigation parameters (including speeds and coordinates), in the absence of constantly updated real-time information from the SNA, the device is assembled, programmed, debugged and works as follows.

According to the measurements received from a single unit of medium precision CE, each computing platform forms its own navigation solution. In this case, the first platform is used only for determining pitch and roll angles, while the second provides the calculation of the heading angle, ground speed (and its projections) of the carrier and the geographical coordinates of the carrier.

Figure 2 presents the functional diagram of the first computing platform. This is a basic platform that works in its basic units for calculating accelerations, calculating speeds, the first and second quaternion blocks, the unit for calculating the matrix of guiding cosines and orientation angles. Using the values of the angular velocities ω _b measured by the TLS of block 1, the elements of the quaternion of the final rotation from the coupled coordinate system to the inertial one (block 11) and then from the inertial coordinate system to the navigation one (block 12) are calculated. Using the elements of the second quaternion (block 12) of the final rotation (q _0, q ₁ , q _2, q ₃ ) ₁ in block 13, the matrix elements of the guide cosines of the transition from the connected coordinate system to the navigation are calculated and the orientation angles (pitch, roll) are calculated in the block 13 according to the elements of the matrix of guide cosines. Elements of the second quaternion are also used in the first block of quaternion calculations 11 in the next step of discrete calculations.

. Затем в блоке 9 осуществляют вычисление линейных и угловых скоростей навигационной системы координат, в том числе путем интегрирования (примечание: напрямую интегрирование осуществляется только при расчете линейных скоростей по ускорениям. Эти формулы имеют общий характер и применяются во всех навигационных системах). Рассчитанные угловые скорости поступают на второй вход кватернионного блока 12 (примечание: расчет кватернионов описан в многочисленной литературе).In block 8, using the matrix of guide cosines from block 13, the accelerations a _b measured by the accelerometers of block 1 are converted to the navigation coordinate system

. Then, in block 9, linear and angular velocities of the navigation coordinate system are calculated, including by integration (note: direct integration is carried out only when calculating linear velocities from accelerations. These formulas are general in nature and are used in all navigation systems). The calculated angular velocities arrive at the second input of the quaternion block 12 (note: the calculation of quaternions is described in numerous literature).

(их составляющие) далее раздельно поступают во вторые блоки вычисления кватернионов - соответственно в блоки 12 и 18.The second one works similarly to the first computing platform, but it has a significant difference in the formation of damping signals. However, although the implementation of damping in blocks 10 and 16 is different, in both platforms their generated damping signals

(their components) are then separately sent to the second blocks of the calculation of quaternions - respectively, to blocks 12 and 18.

Для демпфирования используют

- разность проекций инерциального ускорения a_N навигационной системы координат и ускорения, рассчитанного по показаниям СВС, и подают на третий вход второго блока 12 кватернионных вычислений по формулам с пропорциональной и интегральной составляющими:In the first platform for the implementation of the damping signals in block 10, according to the signals from block 2 of the SHS and block 8, the airspeed accelerations are calculated, after which they are smoothed by a first-order low-pass filter of the type

For damping use

- the difference between the projections of the inertial acceleration a _{N of the} navigation coordinate system and the acceleration calculated according to the SHS readings, and is fed to the third input of the second block 12 of quaternion calculations by the formulas with proportional and integral components:

,

,

,

- проекции скорости

для демпфирования ошибок первой платформы;Where

,

- projection of speed

for damping errors of the first platform;

K, K ^b - damping parameters (coefficients).

The damping implemented in this way guarantees a sufficiently accurate calculation of pitch and roll angles, but it is not suitable for sufficiently accurate determination of speeds and geographical coordinates (note: to calculate geographic coordinates, the transition matrix from the ground-based coordinate system to the navigation is calculated and geographical coordinates are calculated from its elements )

For a sufficiently accurate determination of the components of the velocity of the carrier and its geographical coordinates (in the absence of signals from the SNA), another damping law is used, implemented in the second platform. Fig. 3 shows a functional diagram of a second platform. Here, the communications and blocks coincide in many respects with the first computing platform, with the exception of the implementation of the block for generating damping signals (block 16) and correction of the current heading angle (using the signal from block 6 for determining the heading error) in the second block of quaternion calculations (block 18).

In order to be able to calculate the velocities and coordinates in the integrated (joint) with the SHS mode, it is necessary to use damping by the difference between the inertial speed relative to the Earth and the speed calculated from the SHS readings, but for this it is necessary to know (at a minimum) constantly stored values (estimates) of the wind speed and direction , which is proposed to be implemented in this invention.

In this case, the low-frequency (smooth) change in wind speed will not affect the accuracy of the system in the time interval of the order of 40 ... 60 minutes, since it will differ little from the constant stored value. Whereas a relatively sharp (high-frequency) change in wind speed will be counteracted by the damping circuit by reducing the damping coefficients, which ensures damping attenuation. In fact, damping in this case will play the role of a low-pass filter. Such an approach is possible only in the case where CEs have accuracy, at least at the level of medium accuracy systems, and cannot be used for low-current systems with “rough” CEs (as, for example, in the prototype). Note that medium-precision systems include CEs with gyro drift parameters of 0.5 ... 2.0 deg / s and accelerometer zero offsets of 10 ^-4 g ... 5 · 10 ^-4 g.

The second platform for damping uses the difference of the projections of the velocity V _{2 of the} inertial navigation system (INS) of the carrier relative to the Earth (block 15), the projections of the air speed calculated (in block 16) from the SHS and the stored estimates of the components of the wind speed (block 7), calculated using the SNA to the beginning of the autonomous mode (with the absence of SNA signals) reckoning of the second platform:

δV _N = V _N2 -V _b cosH ₂ -U _N ;

δV _E = V _E2 -V _b sinH ₂ -U _E.

Here, the course angle H ₂ is taken from block 19.

, далее поступающего на вход второго кватернионного блока 18. Проекции демпфирующего сигнала

формируют следующим образом:This speed difference, implemented by the adders 20, 21, is fed to the input of the first integrator in the block for calculating linear and angular velocities (block 15); and also serves in the block signal generation damping 16 for the formation of a damping signal

further arriving at the input of the second quaternion block 18. Projections of the damping signal

form as follows:

In block 16 is also calculated using the heading signal H ₂ from block 19 of the projection of air speed V _b from the SHS on the axis of the navigation coordinate system, then fed to the input of the first adder 20:

;

;

.

.

In order to calculate the speed of an object relative to the Earth by measured airspeed, it is necessary to determine the projection of the wind speed onto the navigation coordinate system (block 7), and also to determine the error in the course calculation (block 6).

To obtain estimates of the projections (components) of the wind speed U _N , U _E in block 7, use the following equations:

UN = V _N -V _b cosH;

U _E = V _E -V _b sinH,

where V _ss = (V _N , V _E ) - projection of speed relative to the Earth received from the SNA,

H is the heading angle, which is calculated and stored in block 19 after determining the heading angle error and its correction.

в блоке 6 используют разность сигнала скорости СНС V_снс=(V_N, V_E) и инерциальной вычисленной скорости V₂=(V_N2, V_E2) (см. Фиг.1). Эту разность подают на вход фильтра Калмана в блоке 6, где в качестве модели используют уравнения ошибок ИНС, связывающие ошибки скорости, ошибки курса и собственные погрешности датчиков ЧЭ.To determine a course error

in block 6, the difference of the SNA speed signal V _ss = (V _N , V _E ) and the inertial calculated speed V ₂ = (V _N2 , V _E2 ) are used (see Figure 1). This difference is fed to the Kalman filter input in block 6, where the ANN error equations connecting velocity errors, course errors, and intrinsic errors of the SE sensors are used as a model.

From the entire set of equations it follows that using the components of the wind speed and air speed, it is possible to determine the speed of the object relative to the Earth in the absence of true signals from the SNA (primarily in the presence of active interference of any type for SNA jamming).

Phased timing diagram of the operation of the entire system is presented in Figure 4.

Before takeoff, while the aircraft is stationary, the system is set to the horizon (the initial angles of roll and pitch are determined). After the take-off of the aircraft, a rough, then accurate, azimuthal display is carried out (heading error in block 6 is determined) using the SNA signals and, in parallel, the wind speed is determined in block 7 using the SNA and SHS. After which the SNA can be turned off and the system can go offline using only the SHS.

It is important to note that in the case of a satisfactory SNA signal, the system is always in integrated mode with the SNA, and only if there is a failure of the SNA (in the presence of jamming) does the system switch to the proposed autonomous reckoning mode from the SHS. In this case, blocks 6 and 7 update their signals only in the integrated mode with the SNA, and when switching to offline mode, the last updated values are stored in blocks 6 and 7, which are then used in the calculations of the offline mode.

This technical device was implemented by TeKnol LLC (Russia) in the serial product KompaNav-5 and passed a complete series of flight tests on various types of aircraft. Figure 5 presents the errors of the ANN in offline mode in the absence of signals from the SNS in the traditional and proposed systems. A traditional system with sensors (SE) of the same average accuracy will determine the current geographical coordinates at the level of 50 ... 60 nautical miles, which is 40 ... 50 times worse than in the proposed CompaNav-5 system.

Claims (1)

A small-sized strap-down inertial navigation system of medium accuracy, correctable from an air signal system, containing a block of sensitive elements (SE) of medium accuracy, consisting of three accelerometers and three angular velocity sensors along three orthogonal axes, two computing platforms, an air signal system, and a heading error determination unit and a unit for determining wind speed; communication with the satellite navigation system, while the outputs of the linear acceleration signals of accelerometers and angular velocities of the SE block, as well as the output of the air signal system, respectively, are connected to the first, second and third inputs of the first and second computing platforms, the output of the air signal system is also connected to the first input of the block determination of wind speed; the satellite navigation system is connected to the first input of the heading error determination unit and to the second input of the wind speed determining unit, the output of which is connected to the fourth input of the second computing platform, the output of which is connected by the speed of the medium to the second input of the heading error determining unit, the output of which is connected to the fifth input the second computing platform, the outputs of which are the outputs of the system in the course angle, the speed of the medium and its geographical coordinates, and the outputs of the first platform are the outputs of the system at the corners of the pitch and roll of the carrier; as part of the first computing platform, its own block for converting accelerations from the coordinate system connected to the navigation system, its own block for calculating the linear and angular velocities of the navigation coordinate system, its own block for generating damping signals, its first and second blocks for quaternion calculations, its own block for computing the matrix of guiding cosines and orientation angles ; own connection with the air signal system; wherein the output of the linear acceleration signals of the accelerometers of the SE unit is connected to the first input of the acceleration conversion unit, the output of which is connected to the input of the speed calculation unit of the navigation coordinate system and the first input of the damping signal generation unit; the output of the angular velocity signals of the SE block is connected to the first input of the first quaternion block, the output of which is connected to the first input of the second quaternion block; the second and third inputs of which are connected respectively to the output of the speed calculation unit of the navigation coordinate system and to the output of the damping signal generation unit; the output of the second quaternion block is connected to the input of the block calculating the matrix of guide cosines, as well as in feedback with the second input of the first quaternion block; the first feedback output of the computing block of the matrix of guide cosines is connected to the second input of the acceleration conversion unit; the output of the air signal system is connected to the second input of the damping signal generation unit; the second and third outputs of the block of calculation of the matrix of guide cosines are the outputs of the first computing platform and the entire system at the pitch and roll angles of the carrier; as part of the second computing platform, its own unit for converting accelerations from the coordinate system connected to the navigation system, its own unit for calculating linear and angular velocities and geographical coordinates, its own unit for generating damping signals, its first and second blocks for quaternion computing, its own unit for computing the matrix of guiding cosines and orientation angles ; its connections with the airborne signal system, with the unit for determining wind speed and with the unit for determining heading error; wherein the output of the linear acceleration signals of the accelerometers of the CE unit is connected to the first input of the acceleration conversion unit, the output of which is connected to the first input of the speed and coordinate calculation unit; the output of the angular velocity signals of the SE block is connected to the first input of the first quaternion block, the output of which is connected to the first input of the second quaternion block, the second, third, and fourth inputs of which are connected respectively to the first output of the block of speed and coordinate calculations; with the first output of the damping signal generating unit and with the output of the heading error determination unit; the output of the second quaternion block is connected to the input of the block calculating the matrix of guide cosines, as well as in feedback with the second input of the first quaternion block; the feedback output of the computing block of the matrix of guide cosines is connected to the second input of the acceleration conversion unit; the output of the air signal system is connected to the first input of the damping signal generation unit; the output of the block for computing the matrix of guide cosines along the angle of the carrier course is connected to the input of the block for determining wind speed and to the second input of the block for generating damping signals; the signal of the projections of airspeed according to the SHS is fed from the second output of the damping signal generation unit to the first input of the first adder, the second input of which is connected to the output of the stored estimates of the projections of the wind speed of the wind speed determination unit, and the output of the first adder is connected to the first input of the second adder whose input with a minus sign is the signal of projections of the carrier speed from the second output of the unit for calculating speeds and coordinates; and the output of the second adder is connected to the third input of the damping signal generation unit and to the second input of the speed and coordinate calculation unit, the second and third outputs of the speed and coordinate calculation unit, respectively, from the projections of the medium speed and the geographical coordinates of the medium, as well as the output of the block calculation matrix of the guide cosines in the angle of the carrier course are the outputs of the second computing platform and the entire system.

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